Year	% net
1974	51.10654
1975	56.5577
1976	58.42331
1977	58.84994
1978	60.31859
1979	61.54287
1980	64.11737
1981	61.87091
1982	61.69412
1983	61.98826
1984	61.58252
1985	62.93157
1986	63.72609
1987	64.65902
1988	66.2103
1989	65.50445
1990	66.22127
1991	67.45855
1992	67.45069
1993	66.3291
1994	68.11044
1995	69.72886
1996	71.33341
1997	72.89267
1998	73.83379
1999	75.15947
2000	75.12039
2001	75.89374
2002	76.34238
2003	75.95836
2004	77.97097
2005	77.72204
2006	77.75287
2007	78.0548
2008	77.98414
2009	77.68492
2010	77.27449
2011	77.78273
2012	76.853
2013	76.36018
2014	76.58962
2015	75.81048
2016	76.8629
2017	76.79861
2018	76.90783